clang-format: Update to match docs repo

Update the .clang-format file.
Now includes header sorting and updating PointerAlignment.

Change-Id: I7119c12f1cc0a461cb7e4576dff6a02dcc95cbc4
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/serialize.hpp b/serialize.hpp
index 5198847..e8860f3 100644
--- a/serialize.hpp
+++ b/serialize.hpp
@@ -1,5 +1,7 @@
 #pragma once
 
+#include <string>
+
 namespace openpower
 {
 namespace software